1. Field of the Invention
The present invention relates to a computer pointing device, and more particularly, to a pointing device for controlling scrolls of a screen image.
2. Description of the Prior Art
A traditional pointing device commonly uses a rolling wheel rotatable along a front-and-rear direction to scroll a screen image. It comprises a vertical sensor installed below the rolling wheel for detection of its movements. The rolling wheel comprises a chassis installed on a top side of a mouse and can be clicked to trigger the vertical sensor. The vertical sensor is used for generating control signals such as a page mode scrolling command or a line mode scrolling command. However, the rolling wheel has a very complicated mechanical and electrical interface.
For continuous scrolling of the screen image, the user must repeatedly rotate the rolling wheel. In addition, the rolling wheel must be pressed down in order to trigger a different control mode. The action of simultaneously pressing down the rolling wheel while repeatedly moving it in order to trigger a different control mode is a difficult action to perform for the user.